mil 0.3.2

Intermediate language for the MelVM
Documentation 
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use crate::types::{ExpandedBuiltIn, MelExpr, PushB, PushI, Value};
use std::fmt;
use tap::{Pipe, Tap};
use themelio_stf::melvm::opcode::OpCode;

#[derive(Clone, Default)]
pub struct BinCode(pub Vec<OpCode>);

impl fmt::Display for BinCode {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "{}",
            self.0
                .iter()
                .fold(String::from(""), |acc, bit| acc + &format!("{:02x?}", bit))
        )
    }
}

pub trait Compile {
    /// Produce MelVM interpretable binary from a data type. Consumes a binary struct
    /// and mutates for efficient allocation.
    fn compile_onto(&self, b: BinCode) -> BinCode;

    // Map on the output of the
    // fn map(&self, other: impl Fn(BinCode) -> BinCode) -> BinCode
}

impl<T: Compile> Compile for ExpandedBuiltIn<T> {
    fn compile_onto(&self, b: BinCode) -> BinCode {
        match self {
            ExpandedBuiltIn::Add(e1, e2) => compile_op(b, OpCode::Add, vec![e1, e2]),
            ExpandedBuiltIn::Sub(e1, e2) => compile_op(b, OpCode::Sub, vec![e1, e2]),
            ExpandedBuiltIn::Mul(e1, e2) => compile_op(b, OpCode::Mul, vec![e1, e2]),
            ExpandedBuiltIn::Exp(e1, e2, k) => compile_op(b, OpCode::Exp(*k), vec![e1, e2]),
            ExpandedBuiltIn::Div(e1, e2) => compile_op(b, OpCode::Div, vec![e1, e2]),
            ExpandedBuiltIn::Rem(e1, e2) => compile_op(b, OpCode::Rem, vec![e1, e2]),

            ExpandedBuiltIn::And(e1, e2) => compile_op(b, OpCode::And, vec![e1, e2]),
            ExpandedBuiltIn::Or(e1, e2) => compile_op(b, OpCode::Or, vec![e1, e2]),
            ExpandedBuiltIn::Xor(e1, e2) => compile_op(b, OpCode::Xor, vec![e1, e2]),
            ExpandedBuiltIn::Print(e) => compile_op(b, OpCode::Print, vec![e]),
            ExpandedBuiltIn::Not(e) => compile_op(b, OpCode::Not, vec![e]),
            ExpandedBuiltIn::Eql(e1, e2) => compile_op(b, OpCode::Eql, vec![e1, e2]),
            ExpandedBuiltIn::Lt(e1, e2) => compile_op(b, OpCode::Lt, vec![e1, e2]),
            ExpandedBuiltIn::Gt(e1, e2) => compile_op(b, OpCode::Gt, vec![e1, e2]),
            ExpandedBuiltIn::Shl(e1, e2) => compile_op(b, OpCode::Shl, vec![e1, e2]),
            ExpandedBuiltIn::Shr(e1, e2) => compile_op(b, OpCode::Shr, vec![e1, e2]),

            ExpandedBuiltIn::ItoB(e) => compile_op(b, OpCode::ItoB, vec![e]),
            ExpandedBuiltIn::BtoI(e) => compile_op(b, OpCode::BtoI, vec![e]),
            ExpandedBuiltIn::TypeQ(e) => compile_op(b, OpCode::TypeQ, vec![e]),

            ExpandedBuiltIn::Dup(e) => compile_op(b, OpCode::Dup, vec![e]),
            //ExpandedBuiltIn::Oflo => compile_op::<MelExpr>(b, OpCode::Oflo, vec![]),
            ExpandedBuiltIn::Vref(e1, e2) => compile_op(b, OpCode::VRef, vec![e1, e2]),
            ExpandedBuiltIn::Vappend(e1, e2) => compile_op(b, OpCode::VAppend, vec![e1, e2]),
            ExpandedBuiltIn::Vempty => compile_op::<MelExpr>(b, OpCode::VEmpty, vec![]),
            ExpandedBuiltIn::Vlen(e) => compile_op(b, OpCode::VLength, vec![e]),
            ExpandedBuiltIn::Vslice(e1, e2, e3) => compile_op(b, OpCode::VSlice, vec![e1, e2, e3]),
            ExpandedBuiltIn::Vset(e1, e2, e3) => compile_op(b, OpCode::VSet, vec![e1, e2, e3]),
            ExpandedBuiltIn::Vpush(e1, e2) => compile_op(b, OpCode::VPush, vec![e1, e2]),
            ExpandedBuiltIn::Vcons(e1, e2) => compile_op(b, OpCode::VCons, vec![e1, e2]),

            ExpandedBuiltIn::Bref(e1, e2) => compile_op(b, OpCode::BRef, vec![e1, e2]),
            ExpandedBuiltIn::Bappend(e1, e2) => compile_op(b, OpCode::BAppend, vec![e1, e2]),
            ExpandedBuiltIn::Bempty => compile_op::<MelExpr>(b, OpCode::BEmpty, vec![]),
            ExpandedBuiltIn::Blen(e) => compile_op(b, OpCode::BLength, vec![e]),
            ExpandedBuiltIn::Bslice(e1, e2, e3) => compile_op(b, OpCode::BSlice, vec![e1, e2, e3]),
            ExpandedBuiltIn::Bset(e1, e2, e3) => compile_op(b, OpCode::BSet, vec![e1, e2, e3]),
            ExpandedBuiltIn::Bpush(e1, e2) => compile_op(b, OpCode::BPush, vec![e1, e2]),
            ExpandedBuiltIn::Bcons(e1, e2) => compile_op(b, OpCode::BCons, vec![e1, e2]),

            ExpandedBuiltIn::Jmp(n) => b.tap_mut(|b| b.0.push(OpCode::Jmp(*n))),
            ExpandedBuiltIn::Bez(n) => b.tap_mut(|b| b.0.push(OpCode::Bez(*n))),
            ExpandedBuiltIn::Bnz(n) => b.tap_mut(|b| b.0.push(OpCode::Bnz(*n))),
            ExpandedBuiltIn::Store(idx) => b.tap_mut(|b| b.0.push(OpCode::StoreImm(*idx))),
            ExpandedBuiltIn::Load(idx) => b.tap_mut(|b| b.0.push(OpCode::LoadImm(*idx))),
        }
    }
}

// Compile the args, then append the op (postfix)
fn compile_op<T: Compile>(b: BinCode, opcode: OpCode, args: Vec<&T>) -> BinCode {
    let mut b = args
        .iter()
        .rev()
        .fold(b, |b_acc, arg| arg.compile_onto(b_acc));
    b.0.push(opcode);
    b
}

impl Compile for MelExpr {
    fn compile_onto(&self, b: BinCode) -> BinCode {
        match self {
            MelExpr::Hash(n, e) => e.compile_onto(b).tap_mut(|b| b.0.push(OpCode::Hash(*n))),
            MelExpr::Sigeok(n, e1, e2, e3) => e3
                .compile_onto(b)
                .pipe(|b| e2.compile_onto(b))
                .pipe(|b| e1.compile_onto(b))
                .tap_mut(|b| b.0.push(OpCode::SigEOk(*n))),
            MelExpr::Loop(n, e) => {
                let inner = e.compile_onto(BinCode::default());
                b.tap_mut(|b| b.0.push(OpCode::Loop(*n, inner.0.len() as u16)))
                    .tap_mut(|b| b.0.extend(inner.0.iter().cloned()))
            }
            // Integers evaluate to themselves (push onto stack)
            MelExpr::Value(v) => match v {
                Value::Int(n) => b.tap_mut(|b| b.0.push(OpCode::PushIC(*n))),
                Value::Bytes(bytes) => b.tap_mut(|b| b.0.push(OpCode::PushB(bytes.clone()))),
            },
            // Compile each expression in sequence
            MelExpr::Seq(l) => l.iter().fold(b, |b_acc, expr| expr.compile_onto(b_acc)),
            // Compile the op wth args in postfix
            MelExpr::BuiltIn(op) => op.compile_onto(b),
            MelExpr::Noop => b.tap_mut(|b| b.0.push(OpCode::Noop)),
        }
    }
}

/// Opcode mapping
impl From<PushI> for u8 {
    fn from(_: PushI) -> u8 {
        0xf1
    }
}
impl From<PushB> for u8 {
    fn from(_: PushB) -> u8 {
        0xf0
    }
}

#[cfg(test)]
mod test {
    /*
    fn compile(code: &str) -> Result<BinCode, ()> {
        // Parse
        let (_, ast) = parser::expr(&code[..])
            .map_err(|_| ())?;

        let empty = BinCode(Vec::new());
        Ok( ast.compile_onto(empty) )
    }

    /// Compile a str of code and disassemble back into ops using melVM.
    fn to_ops(code: &str) -> Result<Vec<OpCode>, ()> {
        let bin = compile(code)?;
        Covenant(bin.0).to_ops().ok_or(())
    }
    */

    // fn assert_veq<T: PartialEq + std::fmt::Debug>(v1: Vec<T>, v2: Vec<T>) {
    //     v1.iter().zip(v2.iter()).for_each(|(x, y)| assert_eq!(x, y))
    // }

    /*
    #[test]
    fn cons_a_vec() {
        let bin = compile("(cons 1 (nil))")
            .unwrap();

        assert_eq!(
            format!("{}", bin),
            "f100000000000000000000000000000000000000000000000000000000000000015254");
    }
    */

    /*
    #[test]
    fn vec_len() {
        let ops = to_ops("(len (cons 2 (cons 1 (nil))))").unwrap();
        let target = vec![PUSHI(U256::from(2)), PUSHI(U256::from(1)), VEMPTY, VPUSH, VPUSH, VLENGTH];

        assert_veq(ops, target);
    }

    #[test]
    fn vec_append() {
        let ops = to_ops("(concat (cons 2 (cons 1 (nil))) (cons 4 (cons 3 (nil))))").unwrap();
        let target = vec![PUSHI(U256::from(2)), PUSHI(U256::from(1)), VEMPTY, VPUSH, VPUSH,
                          PUSHI(U256::from(4)), PUSHI(U256::from(3)), VEMPTY, VPUSH, VPUSH, VLENGTH];

        assert_veq(ops, target);
    }
    */
}